Process for the making of metal moulds for a casting

ABSTRACT

A PROCESS FOR MAKING POROUS METAL MOULDS CHARACTERIZED BY MOULDING AND SOLIDIFYING MATERIAL PREPARED BY MIXING AND KNEADING METAL POWDER AND SODIUM SILICATE WITH METAL PARTICLES AS A MAIN COMPONENT ON A PATTERN SET IN A MOULDING FLASKS SO THAT A SHELL MAY BE FORMED MOSTLY OF THE METAL PARTICLES, REMOVING SAID PATTERN FROM THE MOULDING FLASK AND THEN CASTING MOLTEN METAL ON THE SIDE OF THE ABOVE MENTIONED SHELL, IF NECESSARY WHICH IS ARRANGED WITH EXOTHERMIC AGENT, REVERSE TO THE PATTERN SURFACE SO THAT SAID SHELL AND MOLTEN METAL IS MADE INTEGRAL TO MAKE A METAL MOULD.

Sept. 20, 1971 KUNII 'NAKATA PROCESS FOR THE MAKING OF METAL MOULDS FOR A CASTING Filed Feb. 19, 1969 2 Sheets-Sheet l FIG.

u 3. 3. ll/l/l/lf/l/ff/ n. h h I r/l/////////////-\\\ INVEN'IUR BY Ema/1d 62 6 Sept. 20, 1971 KUN" NAKATA 3,605,85

PROCESS FOR TRE MAKING OF METAL MOULDS FOR A CASTING 2 Sheets-Sheet 2 Filed Feb. 19, 1969 FIG-.7

FIG.8

"I'll"! "I'll \x .fl.

l {wmi 11a mm INVEN'I'UR.

BY Maxi ($4M United States Patent 3,605,855 PROCESS FOR THE MAKING OF METAL MOULDS FOR A CASTING Kunii Nakata, Nagano-shi, Nagano-ken, Japan, assiguor to Gonichiro Nishizawa (Governor of Nagano Prefecture), Nagano-ken, Japan Filed Feb. 19, 1969, Ser. No. 800,681 Claims priority, application Japan, Feb. 26, 1968, 43/ 12,093; July 24, 1968, 43/52,287 Int. Cl. B22c 9/00 US. Cl. 164-23 2 Claims ABSTRACT OF THE DISCLOSURE A process for making porous metal moulds characterized by moulding and solidifying material prepared by mixing and kneading metal powder and sodium silicate with metal particles as a main component on a pattern set in a moulding flask so that a shell may be formed mostly of the metal particles, removing said pattern from the moulding flask and then casting molten metal on the side of the above mentioned shell, if necessar which is arranged with exothermic agent, reverse to the pattern surface so that said shell and molten metal is made integral to make a metal mould.

This invention relates to a process for the making of metal moulds for casting.

A casting process using metal moulds has been already used to cast light alloys and copper alloys and has recently come to be applied to cast cast iron.

However, as the metal moulds to be used for the above mentioned casting process is cast by using a sand mould, there are disadvantages that it must be finished and that therefore much cost and time are required to make such metal moulds high in the dimensional precision.

The present invention is to provide a method of mak ing cheap and accurate metal moulds by eliminating such various disadvantages of the known method of making metal moulds as are mentioned above.

One feature of the present invention is a method of making porous metal moulds characterized by moulding and solidifying a material prepared by mixing and kneading a metal powder and sodium silicate with metal particles as a main component on a pattern set in a moulding flask so that a shell may be formed mostly of the metal particles, removing the above mentioned pattern from the moulding flask and then casting a molten metal on the side of the above mentioned shell reverse to the pattern surface so that the above mentioned shell and molten metal may be made integral to make a metal mould. Thus a porous metal mould strongly bonded by the brazing action of the mixed metal powder is obtained.

Further feature of the present invention is a method of making porous metal moulds characterized by moulding and solidifying a material prepared by mixing and knead ing a metal powder and sodium silicate with metal particles as a main component on a pattern set in a moulding flask so that a shell may be formed mostly of the metal particles, removing the above mentioned pattern from the moulding flask arranging an exothermic agent in the part of the moulded shell from which the pattern has been removed and casting a molten metal on the side of said shell reverse to the pattern surface so that said shell and molten metal may be made integral to make a metal mould. Thus there is obtained a porous metal mould more strongly bonded by the bond by the brazing action of the mixed metal powder and the penetration of the above mentioned molten metal among the metal particles by the heating by the molten metal which becomes to be a back metal by a solidfication later and by the heating Patented Sept. 20, 1971 by the ignition and combustion of the exothermic agent used together.

The metal particles to be used in the present invention are usually steel, alloy steel or cast iron particles.

The size of the metal particles is 150 to 10 mesh.

The metal powder is preferably such mixed powder as a copper and copper alloy powder or nickel alloy powder. In order to make the brazing bond of the metal particles easy, the metal particles to be used may be coated on the surface with a metal easy to braze.

The mixing amount of the sodium silicate to be used in the present invention is less than 3% by weight irrespective of the mole ratio of SiO /Na O and must be increased or decreased in a range less than 3% by weight depending on the mixing amounts of the metal particles and such other additive as is mentioned below. Sodium silicate has an action as of a flux melting at a high temperature and making the brazing bond of the shell consisting of metal particles easy. Further, in order to perfect the brazing bond of the metal particles, they may be mixed or painted with such flux as boric acid or borax.

The back sand to be used in the present invention may be an ordinary casting sand. However, if such sand high in the fluidity as a shell mould sand is used, there will be advantages that a reductive CO gas will be produced in the case of casting a molten metal, will prevent the oxidation of the shell consisting of metal particles and will make the brazing of the metal particles easy and that the said will be easily removed after the casting and the surface of the metal mould will be able to be finished to be smooth.

The molten metal to be used in the present invention heats the shell made of metal particles so that they may be brazed and bonded, becomes a back metal after it solidifies and thus has important actions of preventing the deformation of the shell made of metal particles, elevating its durability and adjusting the thermal conductivity. The material and pouring temperature of the molten metal must be determined by well taking into consideration the thickness of the above mentioned shell and the materials of the metal particles and metal powder. However, generally, a high carbon cast iron is preferable.

The exothermic agent to be used in the above mentioned second invention is a thermit reaction agent of any composition and must be of such composition as will not ignite in the step of preheating the shell made of metal particles but will easily ignite at the temperature of the molten metal that is cast in. The amount of use of such exothermic agent may be such as will compensate the quantity of heat short in the case of heating the shell made of metal particles with the molten metal and may be about 1 g. per cm. of the above mentioned shell.

Examples of the method of the present invention shall be explained with reference to the accompanying drawings in which:

FIGS. 1 to 5 show an order of making a metal mould not using an exothermic agent; and

FIGS. 6 to 8 show an order of making a metal mould corresponding to the above mentioned FIGS. 2 to 4 in the case of using an exothermic agent.

Examples of the method of making metal moulds in the case of using no exothermic agent which are one feature of the present invention shall be explained. In examples, part and percent are by weight.

EXAMPLE 1 As shown in FIG. 1, a pattern 2 is placed on a moulding board 3 and a moulding flask 4 having a lining sand 5 is further mounted on the moulding board 3 to enclose the pattern 2.

Then a material prepared by mixing and kneading parts of steel particles of 65 to 100 meshes, 3 parts of a copper powder of less than 10 microns and 3 parts of sodium silicate (of a molar ratio of 2.7) is moulded to be 10 mm. thick on the pattern which is painted with a vinylic paint as a parting compound. The moulded material is solidified by using a C gas or alcohol to form a shell 1 of the metal particles, then the pattern 2 is extracted (as shown in FIG. 2) and said shell is gradually heated with a burner while removing water until it is heated to about 300 C. After the completion of the heating, the flask 4 containing the shell made of the metal particles is turned by 180 degrees, another moulding flask 7 is fitted to it as shown in FIG. 3 and the part from which the pattern 2 has been removed and the space formed by the moulding flask 7 are charged with a back sand 6.

Then the assembly consisting of the moulding flasks 4 and 7 charged with the back sand 6 as mentioned above is turned and a molten metal 8 is poured into a space formed by the back surface of the shell made of the metal particles and the lining sand 5. Such state is shown in FIG. 4.

After the poured molten metal, for example, cast iron 8 melted at 1500" C. solidifies, the moulding flasks 4 and 7, lining sand and back sand 6 are removed to complete a metal mould 9 as shown in FIG. 5.

EXAMPLE 2 Example 1 was repeated except that the following materials were mixed, kneaded and then moulded to obtain a shell.

Parts Nickel-chromium steel particle of 35 to 65 mesh (C,

0.35%; Ni, 3.0%; Cr, 0.6%; Fe, rest) 100 Brass powder of smaller than 10g, (Cu, 60%; Zn,

40%) Sodium silicate (molar ratio 2.7)

A metal mould made of brazed nickel-chromium steel particles was obtained.

EXAMPLE 3 The following materials were mixed, kneaded and then moulded to obtain a shell as shown in Example 1.

Parts Soft steel particle of to 65 mesh (C content,

0.2% 100 Self-fiuxing nickel alloy powder of smaller than 10 (Ni, 72%; Cr, 12%; B, 2.8%; Si, 4.0%; Fe 3.5%; Co, l%; C, 0.5%; M.P., l,040 C.) 10 Sodium silicate (molar ratio 2.7) 2.2

The preheating temperature of the shell was 450 C. And the temperature of a molten cast iron to be poured was 1,470 C. As a result a brazed and bonded metal mould was obtained.

EXAMPLE 4 The following materials were mixed, kneaded and then moulded to a shell as shown in Example 1.

Parts Cast iron particle of 35 to 60 mesh (C, 2.8%; Si, 1.5%) Brass powder of smaller than 10 (Cu, 60%; Zn,

Sodium silicate (molar ratio 2.7) 2

EXAMPLE 5 A material prepared by mixing and kneading 5% by Weight of copper powder and 2% by weight of sodium silicate with high carbon steel particles of a particle size of about 30 mesh as a main component is moulded to be 10 mm. thick on a pattern 2 as shown in the above mentioned FIG. 1. Methanol (or a carbon dioxide gas or alcohol may be used) is flowed into the moulded material to make sodium silicate gel to make a shell 1 of the metal particles. Then, an exothermic agent 10 is applied to be of a fixed thickness to the surface 11 of the shell 1 made of the metal particles after the pattern 2 is removed as shown in FIG. 6. After the exothermic agent 10 is applied, the abovementioned shell is preheated to prevent the quenching of a later poured molten metal 8 and to immediately burn the exothermic agent 10. This preheating can be carried out by such means as a heating furnace or gas burner. However, the preheating is preferably carried out by means of a heating furnace. It is recognized that the preferable preheating temperature is about 250 C.

The moulding flask 4 containing the shell made of the metal particles and treated as in the above and exothermic agent 10 is turned by 180 degrees, another moulding flask 7 is fitted as shown in FIG. 7 and the part from which the pattern 2 has been removed and the space formed by the moulding flask 7 are charged with a back sand 6.

When the assembly moulded as mentioned above is turned again and a molten metal 8 is poured as shown in FIG. 8 into a space formed by the back surface of the above mentioned shell 1 and the lining sand 5, said shell 1 Will be quickly heated, the exothermic agent 10 on the surface of the shell 11 will ignite and burn, the above mentioned shell 1 will be quickly heated from both sides to a high temperature in a reducing atmosphere, the molten metal 8 will easily penetrate the clearances among the metal particles of the above mentioned shell 1, the respective metal particles will strongly bond together and such metal mould 9 as is shown in FIG. 5 will be completed.

EXAMPLE 6 The following materials were mixed, kneaded and then moulded to obtain a shell as shown in Example 5.

Parts Low carbon steel particle of 35 to mesh (C content, 0.2%) Self-fiuxing nickel alloy powder of smaller than 10 (Ni, 72%; Cr, 12%; B, 2.8%; Si, 4.0%; Fe, 3.5%; Co, 1%; C, 0.5%. M.P.,1,040 C.) 3 Sodium silicate (molar ratio 2.7) 1.5

The provision of an oxothermic agent was carried out as shown in Example 5. The preheating temperature of the shell was 300 C. As a molten metal a ductile cast iron containing 3.5% of carbon and 2.3% of silicon was used at 1,430 C. The exothermic agent was ignited and burned at 10 seconds after the molten ductile cast iron was poured.

As a result, the surfaces of the low carbon steel particles were covered with the self-fluxing nickel alloy and the ductile cast iron was penetrated into cavities between said steel particles and thus a strongly bonded metal mould was obtained.

EXAMPLE 7 The following materials were mixed, kneaded and then moulded to obtain a shell as shown in Example 5.

Parts Nickel-chromium steel particle of 35 to 65 mesh (C,

0.32%; Ni, 3.0%; Cr, 6%; Fe, rest) 100 Nickel-silver powder of smaller than 10 (Cu, 64%; Ni, 18%; Zn, 18%) Sodium silicate (molar ratio 2.7 1.7

The provision of an exothermic agent was carried out as shown in Example 5. The preheating temperature of the shell was 250 C. As a molten metal a ductile cast iron containing 3.3% of carbon and 1.8% of silicone was used at 1,430 C. The exothermic agent was ignited and burned at 13 seconds after the molten ductile cast iron was poured.

As a result, the ductile cast iron was penetrated into cavities between nickel-chromium steel particles and thus a strongly bonded metal mould was obtained.

The metal mould obtained by such method of making metal moulds using an exothermic agent as is explained above is stronger in the bond between the metal particles, have no such defects as cracking and particle dropping and is high in the durablity.

When a metal mould made by the above described method of the present invention and a metal mould made by a conventional molten metal casting were compared with each other by casting tests, it was recognized that the metal mould by the present invention produced no crack even in 300 continuous uses but that the metal mould made by the conventional method produced cracks already in uses. That is to say, it was proved that the metal mould made by the method of the present invention was high in the durability.

What is claimed is:

1. A process for making porous metal moulds including the steps of moulding a material prepared by mixing a metal powder of at least one selected from the group consisting of copper, copper alloy and nickel alloy and having a size of smaller than microns, sodium silicate and metal particles of at least one selected from the group consisting of steel, alloy steel and cast iron having a size of smaller than 10 mesh as a main component and solidifying the material on a pattern set in a moulding flask so that a shell may be formed mostly of the metal particles, removing said pattern from the moulding flask and then casting a molten metal on the side of said shell reverse to the pattern surface so that said shell and molten metal are made integral to make a metal mould.

2. A process as claimed in claim 1 wherein an exothermic agent is arranged in the part of the moulded shell from which said pattern has been removed.

References Cited UNITED STATES PATENTS 918,069 4/1909 Marius et al 16497X 1,632,704 6/1927 Jacobs 164-75X 3,313,007 4/1967 James et al 249X 3,434,182 3/1969 Petersen 249135UX J. SPENCER OVERHOLSER, Primary Examiner J. E. ROETHEL, Assistant Examiner U.S. Cl. X.R. 

